1. Field of the Invention
The present invention relates to a multi-channel signal receiver and multi-channel signal processing technology.
2. Description of the Related Art
In a case of a receiver in a multi-channel broadcasting system selectively receiving broadcasting signals with two different transmission bandwidths such as a Terrestrial digital multimedia broadcasting (T-DMB) signal and a Terrestrial Integrated Services Digital Broadcasting (ISDB-T) signal using one digital processor, there is a need to selectively process only desired signals.
FIG. 1 is a block diagram illustrating a conventional dual channel broadcasting receiver 1200 that simultaneously receives a T-DMB signal and an ISDB-T signal.
A radio frequency (RF) front-end 1000 is constructed by a first RF tuner 1020 receiving the T-DMB signal and a second RF tuner 1030 receiving the ISDB-T signal. The magnitude of the T-DMB signal received through a first antenna 1014 is amplified by a first low-noise amplifier 1001 and noise generated in the amplification process is reduced thereby. The center frequency of the T-DMB signal is generated by a first frequency generator 1005, and the generated center frequency thereof is transferred to a first frequency mixer 1002. The first frequency mixer 1002 receives the T-DMB signal and the center frequency thereof, and lowers the frequency of the T-DMB signal to an intermediate frequency band. The T-DMB signal with the intermediate frequency band is amplified by a first gain amplifier 1003 in magnitude, and the amplified T-DMB signal is transferred to a first channel filter 1004. The first channel filter 1004 eliminates interference signals included in the amplified T-DMB signal from the first gain amplifier 1003, and transfers a signal of a transmission band to a switch 1011.
The magnitude of the ISDB-T signal received through a second antenna 1015 is amplified, and noise generated in the amplification process is reduced by a second low-noise amplifier 1006. The center frequency of the ISDB-T signal is generated by a second frequency generator 1010, and the generated center frequency thereof is transferred to a second frequency mixer 1007. The second frequency mixer 1007 receives the ISDB-T signal and the center frequency thereof, and lowers the frequency of the ISDB-T signal to an intermediate frequency band. The ISDB-T signal of the intermediate frequency band is amplified by a second gain amplifier 1008 in magnitude, and the amplified ISDB-T signal is transferred to a second channel filter 1009. The second channel filter 1009 eliminates interference signals included in the amplified ISDB-T signal from the second gain amplifier 1008, and transfers a signal of a transmission band to the switch 1011.
A reason why two RF tuners 1020 and 1030 are required for the dual channel broadcasting receiver 1200 is because transmission bandwidths of respective channel broadcasting signals differ from each other. For example, in a case of the T-DMB signal, signals of a very high frequency (VHF) band are used and a transmission bandwidth thereof is 2.048 MHz. Meanwhile, in a case of the ISDB-T one-seg signal, signals of an ultra high frequency (UHF) band are used and a transmission bandwidth thereof is 0.43 MHz.
The dual channel broadcasting receiver 1200 transfers one of the T-DMB signal and the ISDB-T signal received through the switch 1011 to an analog to digital converter (ADC) 1012 as an input thereof. A controller 1105 of a digital processor 1100 control a variable sampling frequency generator 1013 to generate a sampling frequency based on a transmission bandwidth of the signal transferred to the ADC 1021. In this case, the sampling frequency based on a transmission bandwidth of each signal is not a specific unique value. Namely, in a Nyquist's sampling theorem, the sampling frequency may be greater than at least twice a transmission bandwidth of a signal to be sampled. The received signal converted into a digital signal by the ADC 1012 is stored in a buffer 1101 of the digital processor 1100, and is divided into in-phase components and quadrature-phase components through an I/Q demodulator 1102. A synchronizing block 1103 transfers a control signal for adjusting time and frequency synchronization of an input signal to a data decoding block 1104. The decoding block 1104 receives the control signal from the synchronizing block 1103 and an output of the I/Q demodulator 1102, adjusts time and frequency synchronization of the received signal, and decodes the received signal. The controller 1105 sets parameters required to receive the T-DMB and ISDB-T signals with different transmission bandwidths in the dual channel broadcasting receiver 1200 and to perform a series of the foregoing procedures, and controls respective function blocks 1011, 1013, 1103, and 1104.
Since transmission bandwidths of the respective signals differ from each other, upon sampling the signals at a digital signal, a sampling frequency should change. Accordingly, a variable sampling frequency generator 1013 is used as a frequency generator of the RF front-end 1000 so that a sampling frequency can change according to respective signals. This complicates the construction of the RF front-end and increases manufacturing costs.